Optical communication is a type of communications means that uses light to transfer information between two points over a distance. Historically, some of the earliest forms of optical communications were performed visually, where an optical transmitter emits light as a coded signal, e.g., a sequence of pulses and/or colored light emissions, and is received by a person who visually interprets the coded optical signal to determine the information. Modern optical communications include use of opto-electronic devices where the optical signal is carried over an optical fiber, referred to as fiber-optic communications.
In fiber-optic communications, an optical transmitter is used to convert an electrical signal into an optical signal to send into the optical fiber and received by an optical receiver to recover the optical signal convert back to an electrical signal. For example, the transmission along the optical fiber can include routing through a cable containing bundles of multiple optical fibers and conditioned using multiple kinds of amplifiers. The light is transmitted by the transmitter in the form of an electromagnetic carrier modulated to carry information to the receiver device through the optical fiber. For example, transmitters in optical fiber links can include light-emitting diodes (LEDs) or laser diodes. Infrared light, rather than visible light, is more commonly used in fiber-optic communications, because optical fibers transmit infrared wavelengths with less attenuation and dispersion. In some examples, the optical signal can be encoded using intensity modulation, where in other examples, optical phase and frequency modulation are used to encode the optical signal.